Kidney transplantation is the optimal treatment for end-stage renal disease (ESRD), including for older patients with ESRD, but the scarcity of donated kidneys has focused interest on allocating transplants to the individuals who benefit the most. The growing and unmet need for kidney transplants is driven by the rising prevalence of ESRD in the United States. ESRD prevalence increased 70% from 1995 - 2005, with an even greater rate of rise among patients over 65 years old. Mortality for ESRD patients on dialysis is markedly elevated. For example, dialysis patients 65 - 69 years old live only 25% as long as individuals of the same age in the general population. Compared to dialysis, kidney transplantation leads to substantial improvements in survival and quality of life at all ages. However, older recipients gain fewer years of life from a kidney transplant compared to younger recipients. As a result, the United Network for Organ Sharing has advanced policy applications that would decrease access to kidney transplantation as patients get older. Collectively, these facts indicate that policy-makers and clinicians urgently need more accurate predictors of mortality among kidney transplant candidates and recipients to optimize the fair and efficient use of organs. The central premise of this grant is that functional status would act as a novel and accurate predictor of survival benefit from kidney transplantation. Recent insights from geriatric medicine reveal a strong relationship between better functional status and longer survival. Functional status can capture the cumulative impact of co-morbidities such as diabetes and vascular disease. Kidney transplant candidates often experience a high rate of morbidities while receiving years of dialysis, leading to temporary de-activation on the list, permanent removal, death, or poor survival after transplantation. Therefore, we will study whether functional status can be used to predict important differences in health between individuals with ESRD awaiting a transplant. Because functional status declines with aging even in healthy populations, we will also examine whether the predictive value of functional status differs between age strata. We propose a retrospective cohort study of kidney transplant candidates and recipients using a novel dataset that links registry data from the United Network for Organ Sharing and a large dialysis provider. The study will have the following specific aims: 1) To determine if functional status predicts survival among kidney transplant candidates and recipients; 2) To assess how age affects the relationship of functional status to survival among kidney transplant candidates and recipients; and 3) To determine if functional status predicts removal or inactivation on the waiting list for a kidney transplant. The results of this study have the potential to inform policy development related to allocating the scarce resource of transplanted kidneys, and to help patients with ESRD and their physicians understand the relative risks and benefits of kidney transplantation for individuals of all ages.